Ground surfaces

ABSTRACT

The invention relates to a method of filling craters or depressions in the ground or for constructing roadways on ground which is not initially capable of supporting loads. A hard synthetic plastic foam is formed in the crater or on the ground, the foam being formed so as to have a bulk weight sufficient to give the foam the necessary strength.

United States Patent 91 Haferkamp et al.

[11] 3,822,955 [451 July 9,1974

[ GROUND SURFACES [75] Inventors: Heinz Haferkamp, Wolfenbuttel;

Giinter Peterson, Lingen/Ems, both [21] Appl. No.: 222,492

[30] Foreign Application Priority Data Feb. 12, 1971 Germany 2106723 [52] US. Cl 404/72, 404/31, 404/134 [51] Int. Cl. E01c 7/00 [58] Field of Search 404/17, 18, 31, 72, 82, 404/100, 134

[56] References Cited UNITED STATES PATENTS 1,015,264 1/1912 Forsyth 404/134 X 2,996,963 8/1961 Stultz et a1 404/100 3,024,711 3/1962 Madison 404/72 X 3,091,551 5/1963 Robertson 117/1055 3,250,188 5/1966 Leonards 404/31 3,272,098 9/1966 Buchholtz et a] 404/32 3,279,334 10/1966 Quartararo 404/31 3,332,245 7/1967 Caron 61/36 R 3,443,386 5/1969 Coulter et al.. 61/36 R 3,651,649 3/1972 Najvar et a1. 61/36 R 3,667,237 6/1972 Dougan 404/31 X OTHER PUBLICATIONS Cellular Plastics," Natl. Academy of Sciences-Natl. Research Council, 1967, pages 3-12 & 253. Plastic Foams: The Physics and Chem. of Prov. Per. and Process Technology Vol. II, Publisher John Wiley & Sons, 1969, pages 218-230.

Primary Examiner-Roy D. Frazier Assistant Examiner-Thomas J. Holko Attorney, Agent, or Firm-Toren and McGeady [57] ABSTRACT The invention relates to a method of filling craters or 'depressions in the ground or for constructing roadways on ground which is not initially capable of supporting loads. A hard synthetic plastic foam is formed in the crater or on the ground, the foam being formed so as to have a bulk weight sufficient to give the foam the necessary strength.

7 Claims, 2 Drawing Figures PAIENIEUJUL 9:924

MUIBFZ EQQQ @QQQE GROUND SURFACES The invention relates to a method of filling and improving undesired craters and depressions in the ground or for constructing roadways on ground which is not initially capable of supporting loads.

Undesired craters and depressions in the ground, for example bomb craters, subsidences and broken dikes must be rapidly and effectively repaired in order to prevent further disasters and, in the case of a roadway, to allow traffic to flow again. In the case of a bomb crater in a road, for example, the crater must be filled in as rapidly as possible. The filling must be firm enough to take the load of the traffic and finally the upper surface of the filling must support a roadway deck which will take the load and is sufficiently resistant to abrasion. The engineering problems are intensified by the fact that the construction usually has to be completed within an extremely brief period of time in order to restore the situation with the least possible delay.

The conventional method for filling undesired craters and depressions in the ground involves the use of costly machines such as bulldozers and graders, for filling the crater with earth, sand and/or rubble. This does not of itself produce a roadway capable of supporting traffic. Vehicles cannot roll over the fill until it has been adequately compacted. The compacting cannot bedone by hand. It is necessary to use special compacting machines, for example vibratory rollers or tampers. Machines of this kind are often not available, particularly when a catastrophe has occurred. Even after the material has been sufficiently compacted traffic still cannot flow until a roadway deck has been laid over the fill. This is a further time consuming operation.

Somewhat similar difficulties arise when it becomes necessary to construct a roadway on ground which is not initially capable of supporting loads, for example sandy or swampy ground into which the wheels of a vehicle sink due to the axle load, the wheels subsequently grinding their way still deeper in due to the looseness of the material.

Before traffic can travel over ground of this kind it is necessary to construct a roadway, a costly and time consuming task. Even then the roadway itself often subsides in the course of time.

The object of the present invention is to provide a process for filling craters, dike breaks and the like extremely rapidly, at comparatively little cost in-regard to materials and machinery, and for laying on the surface of the fill, or on non-load-bearing ground, a durable roadway for vehicles.

To solve this problem the proposal according to the invention consists in that a hard foam, for example of polyurethane, polyvinylchloride or polystyrene is formed in the crater or on the ground, the foam being formed so as to have a bulk or volumetric weight sufficient to give the foamthe necessary strength. The advantages of the process according to the invention consist in that the synthetic plastic foam materials used, for example based on polyvinylchloride, polyurethane and polystyrene, occupy very little space before they are foamed. During the foaming the volume increases, under the influence of the gas producing agent, to a volume up to times the initial volume of the material. The materials for making the foam can easily be transported to the construction site for exam- 2 ple in drums or tank wagons and the foaming process requires comparatively little technical apparatus.

A special advantage obtained is that during the foaming the material penetrates into gaps and cracks in the ground, giving an interlocking effect. The hard foams have sufficient compressive strength to prevent vehicles from seriously bending the roadway downwards or deforming it. If a hard foam such as polyurethane is used at a bulk or volumetric weight of kg/m for the foam, the rolling of wheeled vehicles abrades the surface of the foam. The abrasion can be reduced consid erably by laying reinforcement in the surface. The reinforcement is preferably embedded in the foam to lock it in place. The reinforcement should be easy to transport. Flexible reinforcement mats or mats which can be rolled up are convenient for this purpose. They are not only easy to transport but also very easy ,to lay on the surface of the foam. In many cases a simple wire grating is sufficient.

It is not usually necessary to reinforce the main body of the foam cushion. The upper part of the cushion however, which is stressed in tension, needs to be reinforced. In some cases it is sufficient to lay a roadway mat on the surface of the foam, securing if necessary. A roadway can be constructed on swampy ground by first of all constructing a floating foam base and then laying on top of this a suitable roadway mat, which can if desired be embedded in foam. Alternatively plastic foam of different densities can be used, one of the foams acting as the reinforcement.

The invention will now be described in greater detail on the basis of the two examples represented in the drawing, in which:

FIG. 1 is a vertical section through a crater which has been filled by the process according to the invention; and,

FIG. 2 is a vertical section through a roadway constructed on unstable ground.

In FIG. 1 a crater 3 has an upper diameter of 8 meters, a lower diameter of 3 meters and a depth of 4 meters. The crater has been filled with a hard foam, for example a hard polyurethane foam. This material can be foamed using comparatively simple apparatus. The pre ferred method is the l-shot method, involving prepolymerisation. This method gives a hard foam of good quality, in particular the foam produced has a comparatively high mechanical strength. A further advantage of the one-shot method is that the operating conditions can be varied comparatively easily and the process is largely independent of weather and other ambient influences.

The materials for making the foam are obtainable already prepared, usually in the form of two liquid components which merely need to be mixed together at the construction site, the two components already containing all the necessary additives, for example gasproducing agents, catalysts and stabilisers. Using suitable apparatus and assuming that the volume to be filled is m", the filling can easily be completed within one hour. The mechanical strength of the foam depends on the degree of foaming. A foam with a bulk weight of 50 kg/m is sufficiently strong to withstand constant use over a long period by 45 tons endless track vehicles. A hard foam with a bulk weight of 30 kg/m is strong enough to withstand several crossings during a comparatively short period. In regard to the stronger foam with a bulk weight of 50 kg/m", after several dozen crossings by the heavy vehicles during a comparatively long period the surface of the foam shows a certain amount of abrasion in the form of broken granulate. The layer of broken granulate considerably inhibits further abrasion. When a endless track vehicle is decelerated on the foam by applying the brake the foam has an air-spring effect due to its closed cell structure.

For more demanding traffic requirements the cushion of foam can be given a resistant roadway deck. Assuming that the upper surface 6 of the foam cushion 3 is a little below the lever of the normal ground surface, a number of structural gratings or mats 7 are laid on the surface of the foam cushion, to which they are locked by further application of hard foam. The result is an abrasion resistant roadway deck 9.

The mats 7 consist preferably of profiled steel sheet 3 mm thick. Each mat is l m by l m and can be rolled up. The resulting roadway deck can be used by wheeled vehicles which apply a load of 10 tons per axle.

The hard foam used for the roadway deck is a polyurethane foam with a bulk weight of at least 100 kg/m and at most 300 kg/m, the foam having a correspondingly higher strength. The foam for the roadway deck is applied in the same way as the first foam for the cushion.

lnstead of using a hard foam for the roadway deck, or in addition to the hard foam, the mats 7 can be embedded in a plastic-concrete mixture, for example a polyester-concrete. This material takes to 30 minutes to set, depending on the nature of the additives used. The mixture can if desired contain a quantity of normal agricultural soil or even wet earth containing up to 18 percent of earth. The ratio of earth to polyester resin can be of the order of 5 l. The resulting roadway deck has a compressive strength of 400-700 kp/cm depending on the nature of the soil used, and a bending-tensile strength (transverse strength) of 200 to 300 kp/cm can be expected.

The process according to the invention is suitable not only for filling craters in level terrain, but also for repairing breaks in dikes and for increasing the heights of dikes or the like.

A roadway can be constructed on swampy ground as follows. Assuming a ground which after a few hours of rain has a residual load bearing capacity of only 0.2 kp/cm", a floating embankment 11 is first of all constructed using a hard foam of bulk weight 50 kg/m, the embankment being built up to a height of 0.4 m. This can be done by hand using bucket sized portions and producing a somewhat lumpy structure, which does not however come apart under the load of the traffic.

The upper surface 12 of the hard foam embankment 11 is completed by superposing a roadway deck consisting of reinforcement 13 embedded in hard foam or polyester concrete 14. For the reinforcement 13 the same mats as were described above for the crater can be used. The roadway deck can have a thickness of 0.1 m. The hard foam for the deck can have a bulk weight of kg/m The roadway deck is suitable for use by the heaviest wheeled vehicles.

The process according to the invention has two important advantages. In the first place it allows a roadway to be constructed on non-load-bearing ground, using only a foam plastic, a foam producing device and, if necessary to satisfy greater demands, a reinforcement for the deck. Secondly the process according to the invention make it possible to do this without using parts of fixed dimensions. The process is therefore not limited to particular individual applications but can be used for filling all kinds of craters and depressions in the ground and for constructing all kinds of dikes, embankments and other elevated structures.

We claim:

1. A method for constructing a roadway on flexible subsoil which is initially incapable of independently supporting loads because of its inherent lack of structural rigidity, said method comprising the steps of selecting a site consisting essentially of said flexible, nonrigid subsoil substantially in its entirety, and forming in place at said site directly upon said subsoil a mass which essentially consists substantially in its entirety of hard foam plastic material having a volumetric weight of at least 30 Kg/m, said mass so formed essentially providing the major support of said roadway for sustaining loads thereupon.

2. The method according to claim 1 wherein the foam mass is a material selected from the group consisting of polyurethane, polyvinylchloride, and polystyrene.

3. The method according to claim 1 wherein a rolling mat is embedded in the hard foam mass as a reinforcement element.

4. The method according to claim 3 wherein said rolling mat consists of a profiled steel plate.

5. The method according to claim 3 wherein said rolling mat consists of wire mesh.

6. The method according to claim 1 wherein a second mass of hard foam plastic material is superposed as a reinforcement layer over said first foam mass, said second layer of hard foam material being formed with a volumetric weight greater than the volumetric weight of said first foam mass.

7. A method according to claim 1 wherein said mass is formed in said roadway with a depth of approximately 0.4 meters. 

2. The method according to claim 1 wherein the foam mass is a material selected from the group consisting of polyurethane, polyvinylchloride, and polystyrene.
 3. The method according to claim 1 wherein a rolling mat is embedded in the hard foam mass as a reinforcement element.
 4. The method according to claim 3 wherein said rolling mat consists of a profiled steel plate.
 5. The method according to claim 3 wherein said rolling mat consists of wire mesh.
 6. The method according to claim 1 wherein a second mass of hard foam plastic material is superposed as a reinforcement layer over said first foam mass, said second layer of hard foam material being formed with a volumetric weight greater than the volumetric weight of said first foam mass.
 7. A method according to claim 1 wherein said mass is formed in said roadway with a depth of approximately 4 meters. 